Conventionally, a multilayer capacitor has been widely used so as to achieve smaller size and larger capacitance. In fabricating the multilayer capacitor, ceramic green sheets 3 and 4 respectively coated with inner electrode material layers 1 and 2 made of conductive paste are prepared, as shown in, for example, the plan views of FIGS. 1A and 1B. Then, a plurality of ceramic green sheets 3 and 4 are alternately laminated. The laminated body thus obtained is pressed in the direction of thickness and then, fired. Outer electrodes are then formed on end surfaces of a sintered body to which the inner electrode material layers 1 and 2 are led out.
The inner electrode material layers 1 and 2 formed on the ceramic green sheets 3 and 4 are formed so as to extend from first edges 3a and 4a of the ceramic green sheets 3 and 4 toward second edges 3b and 4b thereof. In addition, the inner electrode material layers 1 and 2 are respectively formed to have such a width that side margin regions 5 having a width of x are left between side edges 3c and 3d and 4c and 4d of the ceramic green sheets 3 and 4 and the inner electrode material layers 1 and 2.
The side margin regions 5 are provided for increasing adhesive properties between the ceramic green sheets located on upper and lower sides of the inner electrode material layers 1 and 2 as well as for preventing the inner electrode material layers 1 and 2 from being exposed to side surfaces of the sintered body after sintering. Consequently, it has been conventionally essential to form the side margin regions 5 having a width of x near side parts of the inner electrode material layers 1 and 2 in the multilayer capacitor.
If the width x of the side margin regions 5 is large, however, the width of the inner electrode material layers 1 and 2 is substantially decreased, to prevent the multilayer capacitor from having a greater capacitance. Consequently, it is preferable that the width x of the side margin regions 5 is small so as to make the multilayer capacitor much smaller in size and larger in capacitance.
On the other hand, in mass-producing the multilayer capacitor, relatively large mother ceramic green sheets 6 and 7 are prepared, as shown in the plan views of FIGS. 2A and 2B. A plurality of mother inner electrode material layers 8 and 9 are respectively formed on respective first major surfaces of the mother ceramic green sheets 6 and 7, and a plurality of mother ceramic green sheets 6 and 7 are alternately laminated. Thereafter, the laminated body obtained in this way is cut at locations corresponding to portions one dot and dash lines A and B shown in FIGS. 2A and 2B, thereby to obtain individual laminated bodies. Then, the individual laminated bodies obtained are fired and a pair of outer electrodes are formed on both end surfaces of the sintered body obtained, thereby to fabricate a multilayer capacitor.
However, in laminating the mother ceramic green sheets 6 and 7 respectively having the plurality of mother inner electrode material layers 8 and 9 formed therein, some shift in lamination is forced to occur. As a result, in each of the laminated bodies after cutting, the inner electrode material layers are liable to be exposed to side surfaces of the laminated body. If the inner electrode material layers are exposed to the side surfaces of the laminated body, inferior withstand voltage and shorting of the inner electrode materials.
Furthermore, even if the inner electrode material are not exposed to the side surfaces of the laminated body, but merely lead to the vicinities of the side surfaces of the sintered body obtained, that is, if the width of the side margin regions 5 shown in FIGS. 1A and 1B is very small, the adhesive strength between respective of upper and lower ceramic layers is not sufficiently high, which causes delamination to occur after sintering.
Additionally, if the above described shift in lamination occurs, the overlapping area of the inner electrode materials becomes smaller than intended, so that there is a possibility that the capacitance value may be made lower than the designed capacitance.
For the above described reasons, it is preferable for the width x of the side margin regions 5 to be small, but width x must be made larger than necessary, which prevents the multilayer capacitor from being smaller in size larger in capacitance. In addition, the variation in capacitance value caused by either a shift in lamination or delamination is liable to occur.